ergo
template_lapack_ladiv.h
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1 /* Ergo, version 3.8, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2019 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
4  * and Anastasia Kruchinina.
5  *
6  * This program is free software: you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation, either version 3 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program. If not, see <http://www.gnu.org/licenses/>.
18  *
19  * Primary academic reference:
20  * Ergo: An open-source program for linear-scaling electronic structure
21  * calculations,
22  * Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
23  * Kruchinina,
24  * SoftwareX 7, 107 (2018),
25  * <http://dx.doi.org/10.1016/j.softx.2018.03.005>
26  *
27  * For further information about Ergo, see <http://www.ergoscf.org>.
28  */
29 
30  /* This file belongs to the template_lapack part of the Ergo source
31  * code. The source files in the template_lapack directory are modified
32  * versions of files originally distributed as CLAPACK, see the
33  * Copyright/license notice in the file template_lapack/COPYING.
34  */
35 
36 
37 #ifndef TEMPLATE_LAPACK_LADIV_HEADER
38 #define TEMPLATE_LAPACK_LADIV_HEADER
39 
40 
41 template<class Treal>
42 int template_lapack_ladiv(const Treal *a, const Treal *b, const Treal *c__,
43  const Treal *d__, Treal *p, Treal *q)
44 {
45 /* -- LAPACK auxiliary routine (version 3.0) --
46  Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
47  Courant Institute, Argonne National Lab, and Rice University
48  October 31, 1992
49 
50 
51  Purpose
52  =======
53 
54  DLADIV performs complex division in real arithmetic
55 
56  a + i*b
57  p + i*q = ---------
58  c + i*d
59 
60  The algorithm is due to Robert L. Smith and can be found
61  in D. Knuth, The art of Computer Programming, Vol.2, p.195
62 
63  Arguments
64  =========
65 
66  A (input) DOUBLE PRECISION
67  B (input) DOUBLE PRECISION
68  C (input) DOUBLE PRECISION
69  D (input) DOUBLE PRECISION
70  The scalars a, b, c, and d in the above expression.
71 
72  P (output) DOUBLE PRECISION
73  Q (output) DOUBLE PRECISION
74  The scalars p and q in the above expression.
75 
76  ===================================================================== */
77  Treal e, f;
78 
79 
80 
81  if (absMACRO(*d__) < absMACRO(*c__)) {
82  e = *d__ / *c__;
83  f = *c__ + *d__ * e;
84  *p = (*a + *b * e) / f;
85  *q = (*b - *a * e) / f;
86  } else {
87  e = *c__ / *d__;
88  f = *d__ + *c__ * e;
89  *p = (*b + *a * e) / f;
90  *q = (-(*a) + *b * e) / f;
91  }
92 
93  return 0;
94 
95 /* End of DLADIV */
96 
97 } /* dladiv_ */
98 
99 #endif
absMACRO
#define absMACRO(x)
Definition: template_blas_common.h:47
template_lapack_ladiv
int template_lapack_ladiv(const Treal *a, const Treal *b, const Treal *c__, const Treal *d__, Treal *p, Treal *q)
Definition: template_lapack_ladiv.h:42